When pressure measurements are made within a human or animal, such as within the vascular system, the physical characteristics of the environment make obtaining accurate measurements more complicated than other fluid pressure measurements. For example, such sensors are generally non-toxic and small, in order to cause as little trauma to the individual as possible. In many cases, it may be necessary for the measuring device to enter the body in one location but to make the pressure measurement in a different location which may be a significant distance away from the point of entry of the device. It may therefore be necessary to deliver the sensor to the location using a delivery device such as a catheter. Such a pressure sensing device must therefore be capable of being transported to a different location using a delivery device and must further be able to transmit data back out of the body. Finally, when the pressure measurements are made within the arterial system, the pressure is not steady but rather is pulsatile, rising and falling to an upper systolic and lower diastolic pressure with each heartbeat, adding further complexity to the pressure measurement process.
For some patients, it is useful to obtain a pressure measurement within the coronary arteries. In particular, when a sclerotic lesion is present within the coronary arteries, pressure measurements made upstream and downstream of the lesion can be used to determine whether or not an intervention, such as angioplasty or stent placement, is required. Because such measurements may be used as a basis for therapy decisions, it is important that they be accurate. However, the very small size of the coronary arteries, which may be about 2 mm, and which may be further narrowed by sclerotic lesions or complicated by the presence of stents, as well as the pulsatile nature of the blood flow, and the need to avoid causing any trauma to these critical vessels, present challenges to designing pressure sensing systems.